The increasing use of battery chargers, switch mode power supplies for computers, electronic ballasts for fluorescent tubes, variable speed electric motor controls and other similar equipment all have the potential to dramatically increase the current waveform distortion of power generated by alternating current sources. These current waveform distortions reduce the ability of a distribution system to transmit power and cause conductive interference with other equipment connected to the source.
Circuits for altering the characteristics of loads as seen by the source and thereby reduce the current waveform distortion have been known for many decades and have been widely used such as capacitors, inductors, synchronous capacitors, motor generator sets, ferroresonant transformers and filter and trap networks made up of these and other passive and active components. The components of these circuits are bulky, cumbersome, expensive, noisy and in general are not responsive to changes in the load requirements.
More recently, a number of prior art inventions have provided mechanisms for providing unity power factor by using switching power supply synchronisation to the input voltage waveform. These mechanisms have not specifically addressed the problems of harmonics and form factor, have been electronically complex and make no provision for introduction of outside signals to alter the current wave form.
In particular, European Patent Application 218,267 first published Apr. 15, 1987 by Kislowski uses a current signal derived from the output as well as internal circulating current to obtain a control signal thus making for complexity and no mention is made of form factor or harmonics.
Wilkinson et al. in U.S. Pat. No. 4,677,366 issued Jun. 30, 1987 use several internal signals into very complex signal management circuitry to obtain unity power factor making no mention of form factor or harmonics.
Bucher in U.S. Pat. No. 4,683,529 issued Jul. 28, 1987 uses complex electronic circuitry to obtain discontinuous or near discontinuous current which necessitates the filtering circuitry mentioned in the reference. No mention is made of form factor or harmonics. By switching between 0 and peak value currents with his system, the capability of providing significant RFI is generated as represented by his FIG. 8, neccessitating the complex filtering components of his FIG. 1.
Nowhere in the prior art is there found a device which in combination:
1) Limits the peak current to RMS value ratio, PA1 2) Provides an in phase quasi sinusoidal current wave form, PA1 3) Maintains virtually continuous current flow with PA1 (a) electrical connector means for interposing the apparatus between the current carrying components of the source and the load; PA1 (b) an electric power rectifier to convert the current flow from alternating to direct; PA1 (c) a current energy storage network to enable decoupling of the load from the source; PA1 (d) an electrical power switching network to direct the flow of energy among the source, said current energy storage network and the load; PA1 (e) at least one current sensor to provide signals concerning source current flow; PA1 (f) at least one voltage sensor to provide signals concerning source voltage levels; PA1 (g) electrical means responsive to said sensor signals which converts these said signals into control signals for said electrical switch network so as to maintain desired parameters of power flow from the source. PA1 (a) electrical connector means for interposing the apparatus between the current carrying components of the source and the load; PA1 (b) a current energy storage network to enable decoupling of the load from the source; PA1 (c) an electrical power switching network to direct the flow of energy among the source, said current energy storage network and the load; PA1 (d) at least one current sensor to provide signals concerning source current flow; PA1 (e) at least one voltage sensor to provide signals concerning source voltage levels; PA1 (f) electrical means responsive to said sensor signals which converts these said signals into control signals for said electrical switch network so as to maintain desired parameters of power flow from the source. PA1 (I) a series electrical power circuit comprising; PA1 (II) a switch control module consisting of; PA1 (I) a series electrical power circuit comprising; PA1 (II) a switch control module consisting of; PA1 (I) a series electrical power circuit comprising; PA1 (II) a switch control module consisting of;
minimum range of variation,
thus providing improvements to the power factor, the current harmonics, current form factor and radio frequency interferance.
It is therefore an object of the invention to provide a means for altering the waveform of the current flow to a rectifier fed direct current load which is less complex.
It is a further object of the invention to provide a means for altering the waveform of the current flow to a rectifier fed direct current load which is less electronically and acoustically noisy and whereby load introduced disturbances into the power source are reduced.
It is a further object of the invention to provide a means for altering the waveform of the current flow to a rectifier fed direct current load whereby the power factor as seen by the power source is adjusted to more desirable levels.
It is a further object of the invention to provide a means for altering the waveform of the current flow to a rectifier fed direct current load whereby the harmonic content of the current supplied by the power source is adjusted to more desirable levels.
It is a further object of the invention to provide a means for altering the waveform of the current flow to a rectifier fed direct current load whereby the form factor of the current supplied by the power source is adjusted to more desirable levels.
It is a further object of the invention to provide a means for altering the waveform of the current flow to a rectifier fed direct current load whereby the load has increased isolation from power source disturbances.
It is a further object of the invention to provide a means for altering the waveform of the current flow to a rectifier fed direct current load which is responsive to changes in other loads
Further and other objects of the invention will be apparent to those skilled in the art from the following Summary of the Invention and Description of a Preferred Embodiment of the Invention